The present invention relates to a pump for fitting to a receptacle, the pump comprising a pump body and an assembly that is movable relative to the body, the assembly comprising a piston bearing in leakproof manner against the body and co-operating therewith to define a pump chamber of variable volume.
French patent No. 2 708 314 discloses such a pump that also includes an elastically deformable membrane outside the pump chamber and arranged to return the moving assembly into its initial position after delivering a quantity of substance.
That pump causes the substance contained in the pump chamber to be delivered as soon as the pressure in the chamber begins to increase due to the moving assembly moving downwards.
There exists a need to have a pump of the pre-compression type enabling substance to be delivered at some predetermined minimum pressure, that can be manufactured at relatively low cost, that is agreeable to use, and that operates reliably.
The present invention seeks specifically to satisfy that need.
In the pump of the invention, the moving assembly comprises a rod possessing an internal passage for delivering the substance contained in the pump chamber, the internal passage opening out into the pump chamber via at least one orifice, and the piston is movable relative to the rod between a pre-compression position in which it closes said outlet orifice(s) and a delivery position in which it releases said orifice(s), the piston being moved from its pre-compression position to its delivery position under the effect of the pressure of substance inside the pump chamber.
In a preferred embodiment, the pump chamber communicates with the inside of the receptacle via a duct which is closed by the moving assembly at the beginning of its stroke for delivering a quantity of substance.
Advantageously, the moving assembly is shaped to engage in leakproof manner in the above-mentioned duct so as to close it.
Advantageously, the membrane comprises a sealing skirt that, at rest, bears in leakproof manner via one face against a corresponding bearing surface of the moving assembly to close an air intake passage formed between the membrane and the moving assembly, said sealing skirt being suitable for moving away from said bearing surface when suction is applied to its opposite face in such a manner as to enable air to enter into the receptacle.
This particular embodiment ensures that substance will not leak out through the air intake passage in the event of a reduction in the pressure outside the receptacle, e.g. due to being transported in an airplane.
The air intake passage is open only when the inside of the receptacle is at a pressure that is lower than the pressure that exists outside it.
Advantageously, the moving assembly has an annular rib to which the membrane is secured, said rib being provided with at least one slot for enabling air to be taken in.
In a particular embodiment, an air intake hole is made through the pump body, said air intake hole being separated from the inside of the pump body by the piston when the moving assembly is in its initial position, the piston enabling communication to take place between the air intake hole and the inside of the pump body above the piston when the moving assembly has moved over a predetermined stroke inside the pump body to reduce the volume of the pump chamber.
This prevents the substance contained in the receptacle from reaching the space that lies between the piston and the membrane, while the pump is at rest.
The piston is preferably fitted onto the rod.
In a particular embodiment, the piston is urged into its pre-compression position by a spring.
Still in a particular embodiment, the piston is arranged to deform elastically so as to release the outlet orifice(s).
In which case, advantageously, the piston has an annular sealing wall suitable for bearing against the pump body and against the rod so as to isolate the outlet orifice(s) of the pump chamber while the chamber is being filled, and an elastically deformable return wall bearing against the rod and suitable for deforming elastically to enable the annular sealing wall to be moved and to enable communication to be established between said outlet orifice(s) and the pump chamber while delivering a quantity of substance.
Advantageously, said return wall is deformed under the effect of the pressure of the substance inside the pump chamber.
The axial section of the piston can be generally xcex- or xcexa3- or X-shaped, for example.
Preferably, the above-mentioned return wall of the piston bears against a shoulder on the rod.
In a particular embodiment, the moving assembly has an end acting as a barb snap-fastened in a housing of the pump body.
The invention also provides a receptacle fitted with a pump as defined above.